Upgrade ColPack bindings, options as strings, systematic tests

[gdalle]

This PR supersedes #19

Source - breaking

• Version bump to 0.5.0
• Removed the very inefficient matrix2adjmatrix: non-symmetric matrices must be handled directly with bipartite coloring methods.
• The coloring method and order must now be given as strings (and not trivial structs). The list of accepted strings can be found here https://github.com/CSCsw/ColPack/tree/master/Examples, and user inputs are checked against said list, with informative errors.

Source - not breaking

• New version 0.4.0 of the ColPack_jll dependency
• Addition of ColPackPartialColoring and ColPackBiColoring in addition to ColPackColoring
• Only ColPackColoring and ColPackPartialColoring are exported, I still don't understand what ColPackBiColoring returns
• Partial column coloring of a CSC matrix is done with partial row coloring of its transpose, which is in the proper CSR format. Unpleasant consequence: partial coloring from a matrix and coloring from a file give different results in general.

Documentation

• Removed outdated tutorial and example
• Improve docstrings with code examples and lists of supported options

Tests

• Removed SparseDiffTools comparison (it may rely on implementation details anyway)
• Add systematic tests that every method and order is supported
• Add exception-throwing tests
• Right now there are no correctness checks, it's hard to do those with so many different coloring methods. Should I add some tests for specific colorings?