Squashed commit of the following:

commit 13fdb518
Author: Jens Korinth <jk@esa.cs.tu-darmstadt.de>
Date:   Fri Mar 2 22:34:38 2018 +0100

    Recognize Tcl errors in Vivado logs

commit 90b74d7c
Author: Jens Korinth <jk@esa.cs.tu-darmstadt.de>
Date:   Fri Mar 2 15:04:11 2018 +0100

    Make ILA debug feature generic for all platforms

    * only get_debug_nets depends on the platform
    * rest moved to platform/common/plugins
    * supporting platforms implement wrapper plugin, see
      platform/zynq/plugins/debug.tcl
    * fixed several other issues, e.g., clock selection
    * closes #132 - no master compositions

commit cc8a2df2
Author: Jens Korinth <jk@esa.cs.tu-darmstadt.de>
Date:   Fri Mar 2 10:57:10 2018 +0100

    Bugfixes in Debug feature

    * added ILA implementation feature on VC709
    * fixed SILA implementation feature on axi4mm
    * fixed renamed pos...