PLOT: fixed "file not read" warn. for empty files

Bug was caused when the respective data file was empty, thus no data was
added to the gnuplot scripts, and gnuplot threw a "file could not be
read" - warning
Fix: Empty data files will cause a zero-line to be added to the gnuplot
script.
PLOT: fixed "multiple wildcards"-warning

Bug: A warning should be thrown if there are 2 or more wildcards in one
mathematical expression of a custom plot. The former check also counted
wildcards used in the naming section of the expression, resulting in a
false warning.
Fix: Counts only wildcards in the actual expression section.
PLOT: fixed non showing functions

Bug: If a plot contained a mathematical expression with wildcard, every
functinon containing a '*' would be removed, due to a
wildcard-replacement attempt on said function.
Fix: Wildcard replacement skips functions as it should.
PLOT: fixed bug witth Type not add to customplots
PLOT: 2nd fix on "Type not added to custompl" bug

Bug: A PlotType set in a PlottingConfig would not have any effect on
custom plots. The previous fix didn't completely resolve the issue.
VIS: monitoring now starts immediately in live mode
VIS: fixed bug with dists/nvls not showing correct

Bug: If a metric had no values, it would cause the metrics distributions
and nodevaluelists to not appear in the dropdown menu of multi scalar
visualizers.
VIS: fixed runtimes not being added correctly

Bug: General Runtimedefinitions in a VisualizerConfig would result in
the runtimes being added to the legend, but not show up in the plot.
This was caused by a mismatching static string being used when adding
runtimes from general configs.
VIS: addition to previous fix + log output removed
VIS: added the field "orderId" for generalConfigs

All generalConfigs in VisualizerConfigs can now have an integer with the
key "orderId". GeneralConfigs will be processed according to their
orderId, starting at 0 and going up. If orderId is unset, the respective
values will be added last.
Note: Any rule with orderId of -1 will be added last. Any other negative
orderId will result in not added values.
PLOT: fixed gnuplot errors with candlestick plots