Added support for xterm 256 colors and 24 bit colors

[JoeMerten]

This PR adds support for esc[38;…m / esc[48;…m for 256 colors and 24 bit foreground / background colors. See also:

• Italic attribute and some others not recognized #89
• Implement full xterm-256color range (probably needs JANSI changes) #44
• https://issues.jenkins-ci.org/browse/JENKINS-24378

Please note, that this needs jansi PR #72 to build & work. I'd increased the jansi version dependency in the pom.xml to 1.14-SNAPSHOT to build locally.

Further, we run into a version bump as described in #95 which leads also to make 256 colors and 24 bit colors don't work (even if we have successfully build and all plugin tests passed).

As I found a way to got it work with Jenkins 1.653 (by just deleting jansi-1.9.jar), I'd found no way to make it work with Jenkins 2.x. As dblock commented in #95, we might have to wait until even the Jenkins guys will pick up the latest jansi changes.

[dblock]

I don't think we want to ship with an unshipped version of 1.14. I am not saying we shouldn't merge this, but we should be careful releasing with this.

[dblock]

... and this doesn't pass build since the SNAPSHOT version is a private one.

[JoeMerten]

Ok, then I just have to wait for:

• jansi #72 became merged
• jansi 1.15 release

Both might take a indefinite period of time.

And after this, I'll:

• change the pom.xml in this PR.
• send a PR to jenkinsci to also change their jansi version in pom.xml

CU next time, Joe.

[dblock]

Thanks Joe!

Maybe release what's on master though? It fixes a number of issues.

[JoeMerten]

In #95, you commented:

… but maybe including JANSI as a built submodule (in a different namespace) is OK?

Could you help me to understand the idea behind this approch?
Then I'll give it a try to make MoreColors work without waiting for Jansi & Jenkins repos (and I could refactor the code as soon as Jansi & Jenkins have been caught up).

[dblock]

I mean checking out the source of Jansi as a git submodule, then bulk replacing the namespace by something internal during the build and using that code.

[JoeMerten]

I'm a bit aware about git submodule because of trouble in the past (but however, I'm not git expert at all).
What about PR #98? I'd tested it even in bleeding edge jenkins 2.50 and it works as expected.

[dblock]

I like it enough. Party on.