Fix Graph loading when Dataset names contain spaces (-> develop)

[in3otd]

Fix #929. Works for me. Please check.

If a Diagram contained a Graph which referenced a variable in a Dataset with a name containing spaces, the Graph loading failed as the simple parsing code was confused by the spaces in the Dataset name.

(supersedes #930)

[in3otd]

I have rebased this on the latest develop since I think it should also go to 0.0.20.

By the way, ccache on OSX seems to work now, even if the hit rate is rather low

$ ccache --show-stats
[snip]
stats updated                       Sun Feb 16 09:34:54 2020
stats zeroed                        Sun Feb 16 09:22:31 2020
cache hit (direct)                   370
cache hit (preprocessed)              18
cache miss                           584
cache hit rate                     39.92 %
[snip]
files in cache                      3017
cache size                         630.0 MB
max cache size                       5.0 GB

they are not better for Linux gcc+autotools build, actually

$ ccache --show-stats
cache directory                     /home/travis/.ccache
cache hit (direct)                   278
cache hit (preprocessed)             306
cache miss                           585
[snip]
files in cache                      2033
cache size                         468.4 Mbytes
max cache size                     512.0 Mbytes

while for the Linux gcc+cmake build things are much better

$ ccache --show-stats
cache directory                     /home/travis/.ccache
cache hit (direct)                   784
cache hit (preprocessed)               7
cache miss                             1
[snip]
cache size                         236.8 Mbytes
max cache size                     512.0 Mbytes

similar for the Linux clang+autotools build

$ ccache --show-stats
cache directory                     /home/travis/.ccache
cache hit (direct)                  1150
cache hit (preprocessed)              74
cache miss                             1
[snip]
files in cache                      4940
cache size                         150.0 Mbytes
max cache size                     512.0 Mbytes

Not sure where the differences between builds come from.