comsit from agramfort
Documentation for tf_dics
Documentation for tf_lcmv
FIX test after default taper number changed

compute_epochs_csd now computes the multitaper transform with 3 instead of 7
tapers and the DICS test results that depended on CSD computation with 7 tapers
started failing. Fixed by specifying multitaper bandwidth corresponding to
previous values (resulting in 7 tapers)
Comment out test failing because of recently commented out code
Baseline parameter - add to tf_dics, modify tf beamformer examples
Tests for tf_dics
Source spectrogram plotting code is now a separate function
FIX/STY Small fixes

Among those:
* Use preload=True when rejecting epochs
Move generate_filtered_epochs to epochs module
Move noise CSD computation out of tf_dics
WIP Improve tf_lcmv API

* Move noise covariance calculation outside of tf_lcmv
* Move data filtering in frequency bands inside tf_lcmv
Small cosmetic changes
Add tstep vs win_length check and test and speed up test_tf_dics
Tiny improvements to tf beamformer examples
ENH Use empty room noise for tf_dics example
ENH Scale computed CSD to allow different time window lengths
ENH Use empty room noise in tf_lcmv example
Use n_fft parameter for CSD computation and in tf_dics
FIX us np.allclose for frequency comparison

Not only does this allow tolerance for numerical issues, but also works for
both np.array and float, whereas (x != y).any() as used previously failed when
x and y were floats.