Option to add table title to dbconfig.js

[MattiasSp]

Fixes #160.

Makes it possible to add a custom title to a search table in dbcobfig.js.

This makes it easier to use Origo Map's Search control option 3 (get all data from the search response). Now it's no longer required to change the underlying table, adding an unnesessary title column with a single value, in order to group results by layer/table.

Config example:

models: {
      [...]
      search: {
        search: {
           tables: [
              {
                 table: 'fastighetsytor',
                 searchField: 'fastighetsbeteckning',
                 schema: 'public',
                 geometryName: 'geom',
                 title: 'Fastigheter',
                 useCentroid: true
              },

Request for feedback: the title column is called simply title in the result at the moment, but should perhaps be renamed to make column name collision less likely. Any suggestions?