* Fixes incorrect US/British::fluid values

* Adds interactibility with Python sympy package
* Several documentation corrections
* Improves build configuration
* Adds examples for expression parsing
* Improves Python implementation data, error handling, & interaction
* Upgrades parser/grammar to bison 3.0
* add (+) unary operator in Python

More portability and static initialization fixes

Major CMake build improvements. Few other small changes and additions.

Fixed major calculator expression precedence and associativity issues.

Also Resolved many build issues.

New Calculator class based on bison/flex. Slight change in interface

Major bug fixed in initialization for runtime registry. This bugfix i…

…s critical

if more than one compilation unit is required where runtime::physical::* has
been included.

First git-based release of physical package following the svn-based r…

…elease last

done publicly with r695.