[Config] improve Config

[ddmler]

• [ ] disabling/enabling notices by levels like CHECK_SAFE/CHECK_BETA/…
• [x] improving documentation regarding analyzers configuration
• [ ] improving notices generated by analyzers to include a better description and a link to a page (in the wiki probably)
• [x] check minimum php version for analyzers

[ddmler]

minimum php versions still needed: Deprecated Function /INI: multiple different versions in the code. (split those up into multiple analyzers?? if yes create new directory for deprecated analyzers))

[ovr]

@ddmler Looks like > check minimum php version for analyzers is implemented now

I change from [ ] to [X] for it

[ddmler]

@ovr yeah missing is deprecated function/ini analyzer with minimum php version.

[Mte90]

I think that also a way to exclude files be very useful.

[kilgaloon]

@Mte90 there is [feature] regarding that #344