ContextSuggester: Adding couple of tests to catch more bugs

A bunch of minor fixes have been included here, especially due
to wrongly parsed mappings. Also using assertions resulted in an
NPE because they were disabled in the distribution.

Closes #5525

Also, there is one last thing, which needs discussing: Currently the default precision is so accurate, that a suggestions will fail, you index the lat/lon `52.363389/4.888695` but search with `52.3633, 4.8886` - I think this is confusing. We should either force people to set a `precision` in the mapping or have less high accuracy.