Unifying GUI

[dominikbach]

Stylises the Matlabbatch more uniformly.

Changes proposed in this pull request:

• common selector functions for items that repeat across modules:

  pspm_cfg_selector_channel
  pspm_cfg_selector_channel_action
  pspm_cfg_selector_data_design
  pspm_cfg_selector_datafile
  pspm_cfg_selector_filter
  pspm_cfg_selector_norm
  pspm_cfg_selector_outputfile
  pspm_cfg_selector_overwrite
  pspm_cfg_selector_python
  pspm_cfg_selector_timeunits

• common dependency creators for 3 types of dependencies: data files, model files, channel index

  pspm_cfg_vout_modelfile
  pspm_cfg_vout_outchannel
  pspm_cfg_vout_outfile

• separate run functions for all cfg functions
• stylistic changes
• removed some deprecated items
• some bugfixes and improvements in the main PsPM functions

[teddychao]

Hi @dominikbach apologies for uploading two commits to this PR.

1. I need to add a comment to src/pspm_cfg/pspm_cfg_data_design_selector.m. This file was not changed in this PR so I have to add something to reveal it in change list for commenting. I only added a space that can be deleted later if you wish.
2. I fixed the conflicts that are caused by PR 659. These changes only attempted to fix the conflicts and have no modifications to any change that is introduced in this PR.

[teddychao]

I approved this PR as the test in GUI at my side seems to operate well. I will continue testing in the PR 721 later. There are minor text adjustments, just please only modify if they are necessary. Thanks.