Add skip flags

[hgschmie]

• build-helper:add-source
• build-helper:add-test-source
• build-helper:add-resource
• build-helper:add-test-resource

Add <skip>true|false</skip> to allow skipping plugin execution.

[slawekjaranowski]

There is an issue #153

[slawekjaranowski]

There is also skipAttach option for attach-artifact
https://www.mojohaus.org/build-helper-maven-plugin/attach-artifact-mojo.html#skipAttach

We can think if we want one name skip option for all goals.

We can also have two options - one global skip for all goals and specific one for each goals.

[hgschmie]

github changed / rewrote the title of this commit. I wrote this all-lowercase. :-(

[slawekjaranowski]

github changed / rewrote the title of this commit. I wrote this all-lowercase. :-(

since is a user name on GitHub, so when we prefix with @ anywhere GitHub try to link to account 😄

[hgschmie]

You could just merge the PR(s) and then make the changes that you feel necessary yourself.

• You asked me to add tests. I did that.
• You asked me to change the property names. I did that.
• Now you ask to make another change...

This is not an academic grading exercise where I am trying to get to a passing grade or something to be "acceptable". It is a contribution of a useful feature to a project that I did in my spare time trying to be helpful to the project. I already spent more time on this than I wanted. I am not spending more time.

If you feel that this is not "production ready" code, then you need someone that gets paid for it to get it to that level.

[slawekjaranowski]

@hgschmie tanks for your works ... I don't to examine you or offend you in any way.
Simply also I do a review in my spare free time and I can make a mistake.

I will care about this PR.