add Convolution component in nnet2

blstm remove bug

enforce minimum segment length

- no lattice re-generation after 1st epoch of sMBR
- the results are now better
- adding auto-selection of queue options for BUT

- supports arbitrary number of languages,
- uses 'multi-task' training with per-language weights (one softmax per language),
- (the decoding script not yet merged)

Unify .gitignore patterns

nnet1: bugfix in MultiTaskLoss,

- in case a task gets 0 frames, use 0.0 as objective value, avoid nan,

Add various tag files to .gitignore

Fixing GCC 4.4  -std=gnu++0x compilation issues

trunk: small bug fix in babel scripts

C++11 (non)compliance fix

Documentation changes related to Git migration

Improving the self-configuration capability of some of the extra tools

Addressing @danpovey comments: svn is still a prerequisite; svn mirror is not maintained; version control paragraph in tutorial_code.dox rewritten.

Documentation changes: added Git tutorial, removed Subversion tutorial and updated multiple references from Subversion to Git and from SourceForge to Kaldi's own web site or GitHub as appropriate.

tedlium: Fixes of the stage variable to run from scratch(unless requested otherwise)