SLB parser syntax enhancements

macroParser::addMacro - added := and ?= assignments
macroParser::expand - added %{A}%, %{A:-b}%, %{A:+b}%, %?A% syntaxes
macroParser::strp - wrapper around strpos
dos2unix moved to functions.php
getSLBDefaults result structure change

    getSLBDefaults: changed result key names
    renderSLBDefConfig: new defaults key
    SLBTriplet::prepareParser: idem
    SLBTriplet::prepareParserForRS: idem
addMacro: unify code duplication
new SLB config generation procedure

instead of calling generateConfig for each triplet instance,
generateSLBConfig for triplet list is being called. This increases
performance ~ by 2.

+ generateSLBConfig: function generates config for entire triplet list
~ buildEntityLVSConfig: use generateSLBConfig
+ $parser_class global. Used instead of calling virtual SLBTriplet::createParser

- SLBTriplet::generateConfig
- SLBTriplet::createParser
- SLBTriplet::prepareParser
- SLBTriplet::prepareParserForRS
- MacroParser::pushdefs
- MacroParser::popdefs