Added metapol rule for policies with treedefs

metapol (MetaPolicies) specify trees of policies. Rule created to assist parsing this special case.
Renamed the PoCoCompiler class to Compiler and changed package name
Split ppol into metapol and pocopol rules.

metapol are policies that specify policy trees.
pocopol are traditional PoCo policies.
Renamed packages to be more descriptive
No longer ignoring IntelliJ IDEA project files
Modified compiler to support updated runtime classes
Added PoCo runtime classes

These are used to support the running of PoCo policies along with AspectJ.
Added PolicyVisitor class

PolicyVisitor walks the parse tree of a policy and outputs the Java code to implement it.
Added IntelliJ IDEA project files