Beginnings of itemised listing of use cases.
Added use cases regarding units, algebraic identifier nature, code generation.
Added use cases for ideas: refactoring and numerical conversion utility.
Initial commit of project intro.

There was some private discussion of previous versions.
Revert "Initial commit of project intro."

This reverts commit 01330fdff6499e7f0ac9c86c6d051bd59249ea7e.
Use "symbol" rather than "algebraic identifier".

Also, added functions to symbol types.
"Validate" at the front makes it easier to find this heading.
Capture comments re maths and units validation depending on secondary spec.
Use case for import/export converted from original text.
Created use case description for installing from original roadmap text.
Added some general notes.
Use cases for installation for various languages, host platforms and target platforms.
Capture ideas re conversion from structure for code generation into use case description.
Usecaseified: Access external namespace data, run simulations.

Also, moved some todo items and other minor changes.
RST whitespace fixes.
RST whitespace fixes.
Draft of process doc now exists.
Added options for serialisation formats.

Andre had suggested options other than just XML.
New use case: undo/redo
Minor: fixed typo