[Eiffel] various enhancements

[jvelilla]

Updated Eiffel code generator.

Added missing language reserved words.
Updated mustache templates to use the latest Eiffel rules to avoid obsolte feature calls and Cat-Calls.
Updated Eiffel configuration files (ecf's)
Updated comments styles.
Updated Travis CI file to use the latest Eiffel compiler.
Updated mustache model template to simplify the generated code.
Updated Eiffel sample.

PR checklist

• Read the contribution guidelines.
• [x} Pull Request title clearly describes the work in the pull request and Pull Request description provides details about how to validate the work. Missing information here may result in delayed response from the community.
• If contributing template-only or documentation-only changes which will change sample output, build the project beforehand.
• Run the shell script ./bin/generate-samples.shto update all Petstore samples related to your fix. This is important, as CI jobs will verify all generator outputs of your HEAD commit as it would merge with master. These must match the expectations made by your contribution. You may regenerate an individual generator by passing the relevant config(s) as an argument to the script, for example ./bin/generate-samples.sh bin/configs/java*. For Windows users, please run the script in Git BASH.
• File the PR against the correct branch: master
• Copy the technical committee to review the pull request if your PR is targeting a particular programming language. @wing328

[jvelilla]

It seems circleci build is failing

mvn --no-snapshot-updates --quiet clean install -Dorg.slf4j.simpleLogger.defaultLogLevel=error

[main] ERROR org.openapitools.codegen.languages.MysqlSchemaCodegen - Invalid database name. '12345' cannot be used as MySQL identifier. Escaped value '12345_db' will be used instead.
[main] ERROR org.openapitools.codegen.utils.ModelUtils - Schema cannot be null in isFreeFormObject check
Dec 02, 2020 8:06:29 PM org.apache.maven.wagon.providers.http.httpclient.impl.execchain.RetryExec execute
INFO: I/O exception (java.net.SocketException) caught when processing request to {s}->https://repo.maven.apache.org:443: Connection reset
Dec 02, 2020 8:06:29 PM org.apache.maven.wagon.providers.http.httpclient.impl.execchain.RetryExec execute
INFO: Retrying request to {s}->https://repo.maven.apache.org:443
Dec 02, 2020 8:06:29 PM org.apache.maven.wagon.providers.http.httpclient.impl.execchain.RetryExec execute
INFO: I/O exception (java.net.SocketException) caught when processing request to {s}->https://repo.maven.apache.org:443: Connection reset
Dec 02, 2020 8:06:29 PM org.apache.maven.wagon.providers.http.httpclient.impl.execchain.RetryExec execute
INFO: Retrying request to {s}->https://repo.maven.apache.org:443
Dec 02, 2020 8:06:29 PM org.apache.maven.wagon.providers.http.httpclient.impl.execchain.RetryExec execute
INFO: I/O exception (java.net.SocketException) caught when processing request to {s}->https://repo.maven.apache.org:443: Connection reset
Dec 02, 2020 8:06:29 PM org.apache.maven.wagon.providers.http.httpclient.impl.execchain.RetryExec execute
INFO: Retrying request to {s}->https://repo.maven.apache.org:443
[ERROR] Plugin org.apache.maven.plugins:maven-shade-plugin:3.2.0 or one of its dependencies could not be resolved: Failed to read artifact descriptor for org.apache.maven.plugins:maven-shade-plugin:jar:3.2.0: Could not transfer artifact org.apache.maven.plugins:maven-shade-plugin:pom:3.2.0 from/to central (https://repo.maven.apache.org/maven2): Connection reset -> [Help 1]
[ERROR] 
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR] 
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/PluginResolutionException

Exited with code exit status 1
CircleCI received exit code 1

[wing328]

Pushed 1d9d673 to fix the CI failure. (travis CI failure not related to this change)