Fix saving of channel names in .sr files.

This closes bug #490.
Minor whitespace fixes.
Example channel names: Consistently use all-caps.

Rename Tx->TX and Rx->RX to be consistent with the other names.
CMakeLists.txt: Fix whitespace, cosmetics.
README: Update status.
INSTALL: Update and fix build requirements.
test: Disable all unit tests for now (all of them are broken).
decoderstack.cpp: Fix incorrect #inludes.
Build system: Fix issue with unit tests, simplify code.

Drop some unneeded lines from test/CMakeLists.txt. Most of the variables
are inherited from the main CMakeLists.txt file. This reduces the amount
of duplicated code and the likelyhood that the two CMakeLists.txt files
get out of sync.

This fixes the following issues when building the unit tests
(related to mixing Qt4 and Qt5 apparently):

  [ 69%] Building CXX object CMakeFiles/pulseview.dir/signalhandler.cpp.o
  [...]/test/__/pv/moc_sigsession.cxx:13:2:
  error: #error "This file was generated using the moc from 4.8.6. It"
   #error "This file was generated using the moc from 4.8.6. It"
    ^
  [...]/test/__/pv/moc_sigsession.cxx:14:2:
  error: #error "cannot be used with the include files from this version of Qt."
   #error "cannot be used with the include files from this version of Qt."
    ^
  [...]/test/__/pv/moc_sigsession.cxx:15:2:
  error: #error "(The moc has changed too much.)"
   #error "(The moc has changed too much.)"
    ^
  [...]/test/__/pv/moc_sigsession.cxx:64:7:
  error: ‘QMetaObjectExtraData’ does not name a type
   const QMetaObjectExtraData pv::SigSession::staticMetaObjectExtraData = {
         ^
  [...]/test/__/pv/moc_sigsession.cxx:70:37:
  error: ‘staticMetaObjectExtraData’ was not declared in this scope
         qt_meta_data_pv__SigSession, &staticMetaObjectExtraData }
                                       ^
  [...]/test/__/pv/moc_sigsession.cxx:
  In member function ‘virtual const QMetaObject* pv::SigSession::metaObject() const’:
  [...]/test/__/pv/moc_sigsession.cxx:79:71:
  error: conditional expression between distinct pointer types
  ‘QDynamicMetaObjectData*’ and ‘const QMetaObject*’ lacks a cast
       return QObject::d_ptr->metaObject ? QObject::d_ptr->metaObject : &staticMetaObject;
                                                                         ^
  [...]/test/__/pv/moc_sigsession.cxx:80:1:
  warning: control reaches end of non-void function [-Wreturn-type]
   }
   ^
  test/CMakeFiles/pulseview-test.dir/build.make:1362: recipe for target
  'test/CMakeFiles/pulseview-test.dir/__/pv/moc_sigsession.cxx.o' failed
  make[2]: ***
  [test/CMakeFiles/pulseview-test.dir/__/pv/moc_sigsession.cxx.o] Error 1
  CMakeFiles/Makefile2:110: recipe for target
  'test/CMakeFiles/pulseview-test.dir/all' failed
  make[1]: *** [test/CMakeFiles/pulseview-test.dir/all] Error 2
  make[1]: *** Waiting for unfinished jobs....
test/CMakeLists.txt: Fix file list, fix -DENABLE_TESTS=y build.

The build is now fixed for -DENABLE_TESTS=y, but re-enabling the
actual unit tests (and potentially other issues) will need more work.
Removed cotire

cotire has proven itself to be counter-productive. It rebuilds the pre-compiled
header after any header in pulseview is modified causes a complete rebuild of
all of PulseView. Also, the pre-compiled header contains a union of all the
includes of all source files, which masks errors where source files are missing
needed includes.
.gitignore: Added .ninja_deps
Session: Renamed files to match class name
Ruler: Moved calculate_tick_spacing into View
View: Make horizontal arrow-key scrolling useful

Currently, the horizontal scroll bar scrolls by a very small amount
of time when the arrow keys on the keyboard are used. This is because
View::horizontalScrollBar's single step size is never set.

In order to make the arrow keys become useful, this patch sets this
step size equal to the major tick width of the ruler. This results
in scrolling by a fair amount of time without losing track of the
context and also preserving the positions of the major ticks on
the ruler when scrolling.
test: Add a dummy unit test to fix 'make test'.

This should be dropped again when the real unit tests
are working again.
connect: Fix filtering of supported devices.

Now that driver options are split from device options, it is not
possible to check the SAMPLERATE option on a driver as it is a device
only option. The SAMPLERATE test still works on some drivers that
didn't have their options split yet, but this won't hold true for long.
The proper way is to check the driver class, which is the only option
you can expect at the driver level for now.
CMakeLists.txt: mingw: Simplify by using Boost_THREADAPI.
Signal: Save and load signal names as UTF-8 strings.

This fixes bug #498.
mingw: Drop libusb0.dll, always use libusb-1.0.