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 OSM-PH and OSM-ID module sprint and discussed in the issue #197.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.

Although this PR will be under my name, this is a collaborative work by:
@dichapabe @emirhartato @adissadis @gitGOwin @jmbangate @schadow1