Static hidden dimensions in wheredim

[lucafavatella]

Implement deterministic hidden dimensions statically in ttransform1 module. Only wheredim is implemented; abstractions/applications are commented out in ttransform1 at the moment.

Most changes are in ttranform1. The following changes are instead across the board:

• Removed constant dimensional query '?' with associated tests as it is unused
• External dimensions are represented as e.g. {dim,"t"}, in order to distinguish them from variable identifiers
• Hidden dimensions are represented as e.g. {dim,{Pos,Idx},"t"}

A test in the ttransform1 module tests the "transform0 -> transform1 -> tcore -> tcache" integration.

Caveats:

• This pull request introduces some XXX comments
• Maybe the logging code in tcache does not play nicely with the format of hidden dimensions
• Abstractions/applications' transformations are to be implemented yet

[lucafavatella]

Ed, I sent this pull request even if abstractions/applications are commented out in ttransform1 as I prefer to get feedback on the implemented changes sooner rather than later.

[lucafavatella]

Updated pull request merging recent master (and adding improvements in tests).