Feature/regex tok trim

[wolliq]

Description

This RegexTokenizer extension proposes the capability of trimming idenitfied tokens so that they can be used in further processing without having to apply others data transformations.
In particular we can trim tokens and decide whether preserve orignal indexes.

Motivation and Context

It has been noticed that RegexTokenizer was missing the token trimming capability.

How Has This Been Tested?

Full non regression test in Scala with added use cases in specific tests suite.
Added tests on Python interface.

Screenshots (if appropriate):

[info] Suites: completed 131, aborted 0
[info] Tests: succeeded 638, failed 0, canceled 0, ignored 5, pending 0
[info] All tests passed.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• Code improvements with no or little impact
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING page.
• I have added tests to cover my changes.
• All new and existing tests passed.