Fix for Krovak +czech default behaviour

[jachym]

If I understand this well, the +czech parameter was not parsed (from EPSG definition).

There was difference between C implementation and JavaScript implementation of the Krovak file, regarding the +czech parameter:

In C:

...
        if( !pj_param(P -> params, "tczech").i )                                
          {
            xy.y *= -1.0;
            xy.x *= -1.0;
          }
...

In JavaScript

		if(this.czech) {
	    		p.y *= -1.0;
	    		p.x *= -1.0;
		}

The difference is, that in C, if +czech is not defined (default), values will be multiplied by -1. In JavaScript the same behaviour occured, when +czech is defined.

This patch makes 3 changes:

• It adds the parser for the +czech parameter
• It modifies the +czech handler according to C proj4
• It modifies EPSG files according to wildly used definition of 102067, according to ​http://grass.fsv.cvut.cz/gwiki/S-JTSK#WGS84_.E2.86.92_S-JTSK

Tests are modified as well (they are working well, but don't forget to rebuild the compressed and uncompressed version of proj4js).

[madair]

patch applied