conf/function.py: completed documentation, functionality

still unresolved: how does the user declare a function?
conf/expr.py: finished Expression subclasses

the classes for representing expressions are now done and fully documented
they correlate directly with the [literal, funccall, varsubst, expressionlist] nonterminals in the 'expresion' rule.
there is also a 'concatenation' class, which correlates to the outer '*' in the 'expression' rule.
grammar.wi: renamed symbols

made singlequoted/doublequoted literals transparent in grammar.wi
conf/boolexpr.py: created abstract base type
tests: removed old shitty conf emulation code
tests: adapted builder test to new conf/util/etc/ structures
dirscanner: better superclass call for targetsmfile
conf: fixed varscopt to assignmentscope variable naming
Merge remote-tracking branch 'origin/tests' into conf
conf/variable.py: fixed addassignment error
conf/config: added OrderedSet import
conf/expr: fixed imports for conf.function
conf/expr: added : to __init__ definition
conf/variable: fixed variable names for result generation
conf/assignment: split up __repr__ output generation
conf/variable: added exception for non-list assignment expressions