Merge pull request #340 from mmklee/templates

Templates for NTL6
removed unneeded templates (already in factory)
fix: do not set minpoly to 0 (in poly.lib)
fix: div for int division
fix: memory leak in intvec::String
fix: more memory leaks (analogue intvec::String)
chg: update grobcov.lib
chg: got rid of Farey in chinrem_gcd
various changes/fixes to documentation
chg: earlier switching to dense gcd
chg: arrange variables by deg if their leading coeff has the same size
fix: error when compiling with --enable-timing
chg: leave Lucks sparse lifting earlier if input is too dense
chg: order of multiplicands if their sizes differ
chg: cut off for Karatsuba
chg: added some timing infos
chg: order of multiplicands