Proposed new category on mobile mapping with SmartPhones

This PR proposes a new section on mapping using smart/mobilephones.  This is a product of the the OSM-PH and OSM-ID module sprint.  The mobilemapping category includes the following of smartphone apps: OSMAnd, OruxMaps, GPS Essentails and OSMTracker.

This PR also includes minor changes to other sections to improve the genration of pdf (https://github.com/essc/learnosmtopdf).  The changes should not affect the actual html rendering of the main learnosm site.

@dichapabe @emirhartato @addisaddis