2 pages view
Merge branch 'master' into 2pages

Conflicts:
	src/org/geometerplus/zlibrary/text/view/ZLTextView.java
fixed column width
Merge branch 'master' into 2pages

Conflicts:
	src/org/geometerplus/zlibrary/text/view/ZLTextView.java
Merge branch 'master' into 2pages

Conflicts:
	src/org/geometerplus/zlibrary/text/view/ZLTextView.java
2 columns: text selection
Merge branch 'master' into 2pages

Conflicts:
	src/org/geometerplus/zlibrary/text/view/ZLTextView.java
Merge branch 'master' into 2pages

Conflicts:
	src/org/geometerplus/zlibrary/text/view/ZLTextViewBase.java
2-column mode options
updated TODO
page numbering in 2-column mode; end-of-section rpocessing in 2-column mode (in progress)
2-column view: fixed end-of-section processing, fixed backward scrolling
max space between columns value => 300
getTextAreaWidth() method has gone; small optimizations