Apply static inline to all methods

[robb]

• [x] ASTAll
• [x] ASTAny
• [x] ASTDefaults
• [x] ASTDifference
• [x] ASTEach
• [x] ASTEmpty
• [x] ASTExtend
• [x] ASTFilter
• [x] ASTFind
• [x] ASTFlatten
• [x] ASTGroupBy
• [x] ASTHead
• [x] ASTIndexBy
• [x] ASTIndexOf
• [x] ASTIntersection
• [x] ASTMap
• [x] ASTMin & ASTMax
• [x] ASTNegate
• [x] ASTPick
• [x] ASTPluck
• [x] ASTReduce
• [x] ASTReject
• [x] ASTShuffle
• [x] ASTSize
• [x] ASTTail
• [x] ASTUnion
• [x] ASTWithout
• [x] Remove ASTConstants.h I ended up introducing a new ASTERISM_OVERLOADABLE in AsterismDefines.h

Refactoring ASTNegate also obviated the need for metamacros.h.

Fixes #20

[robb]

Here's a list of all internal methods, return type omitted for legibility.