Merge pull request #16 from lukechampine/ast

AST reorganization
add error checking to makeplugin
Merge pull request #17 from lukechampine/import

Add support for importing existing scripts
Merge branch 'master' of github.com:mkvsynth/mkvsynth
Merge pull request #22 from lukechampine/memory

Memory management
add generated files
use Value instead of Value* in ASTnode
Valgrind #9: fix invalid plugin reads
reduce fn lookup times and fix recursive fndef warning
add generated file
update documentation
fix chaining
remove boolean constants

defining boolean constants is unnecessary. Originally, they were
included to distinguish between a number and a truth value, but
the valueType enum serves that purpose better.
duplicate fn name when defining
align ASTnode struct -- save 8 bytes
const everything
remove unnecessary includes
ex: free children and place result in p->value
remove strdup() from putVar()
free the result of a statement