GENERALVALUES analysis:
- implemented a nesting analysis for top-level #ifdef branches
    * for each branch (#if/#elif/#else) a maximum nesting depth is determined
    * output is in file 'nesting_degrees_toplevel_branches.csv'
- some minor adjustments, added comments, and refactorings
GENERALVALUES analysis:
- changed preparation process to a new one ('generalvalues') to preserve correct line numbers
Merge branch 'master' of https://github.com/clhunsen/cppstats

Conflicts:
	analyses/generalvalues.py (correction of #else-branch removals)
GENERALVALUES analysis:
- inserted clarifying comments on the collection of the metric values (how often are feature signatures used per project/file)
GENERALVALUES analysis:
As line numbers are not important for output, the preparation can be 'general'.
Line numbers are removed from output for 'nesting_degrees_toplevel_branches.csv'.

This generally reverts commit b21e9657245e9824d97ed6dac41979f10b339218.