HSec plots using basemap are slow to generate

[Joern Ungermann]

Generating plots with coast lines etc. take several seconds. Partially this is due to the Basemap class being instantiated fresh for each plot, which necessitates the reading and processing of all shape files.

Improving this would reduce the server load, increase response time for users, and reduce the time needed for py.test.

[Reimar Bauer]

Added a cache for basemap coastline and country shape data.

See issue #173.

→ <<cset 3322ec909c2c>>

[Reimar Bauer]

Use basemap cache in testcases and documented parameters in configuration sample.

See issue #173

→ <<cset 91836bf1ed1f>>