Add empty pattern generator signal PG_NONE to the list.
Add Pattern Generator signal dictionary
Dictionary: add PG_NONE as "empty" and define PG signal error state.
Accessing a map outside its range does not throw an exception - which is
why try-catch doesn't work here. Check for presence explicitly using
map.find() and return error code otherwise.
API CHANGE: Pattern Generator configurations are now only accepted via the
form pair<string,unit8_t> and will undergo dictionary lookup and additional
checks for consistency. The verifyPatternGenerator function is adapted accordingly.

Multiple signals inside one string can just be concatenated using ";", e.g.
"token;sync" will send PG_TOK+PG_SYNC at once.
Update libpxar version to 1.0.1 and extend API description of the
functions in question.
Adapt tools to make use of new PG setup structure.
Also allow signal "delay" as PG_NONE
Rework scentral pxar UI parts to comply with changed API now using pattern
generator signal strings instead of undescriptive register values.
Adapt PixTestPattern to new Pattern Generator style.
Also remove two times hardcoded default pattern generator.
Adapt PixTestSetup to new pattern generator configuration style
Merge branch 'master' of github.com:psi46/pxar