Removed dummy-missingfiles database

Created a mechanism to return None at certain probability

Propagated the  option --allow-missing-files .....

See merge request !103

Resolve "The new way of using a single configuration file is not tested yet"

Closes #94

See merge request !100

Resolve "The flag 'execute_only' cannot be placed in a config file"

Closes #92

See merge request !99

Resolve "doc/experiments.rst points to deprecated docs location"

Closes #91

See merge request !98

Resolve "matplotlib Invalid DISPLAY variable"

Closes #89

See merge request !97

Resolve "matplotlib Invalid DISPLAY variable"

Closes #89

See merge request !96

Use switch_backend instead, see https://github.com/matplotlib/matplotlib/issues/3466/#issuecomment-270603717

Merge branch '88-there-is-absolutely-no-need-for-having-a-client-class-in-the-filelistdatabase-implementation' into 'master'

Resolve "There is absolutely no need for having a "Client" class in the FileListDatabase implementation"

Closes #88

See merge request !95

Resolve "No way of plotting open-set DIR curves"

Closes #87

See merge request !94

This reverts commit 29448290.

Small corrections to the documentation and command line help

See merge request !93

Merge branch '78-the-documentation-does-not-mention-usage-of-single-configuration-files' into 'master'

Resolve "The documentation does not mention usage of single configuration files"

Closes #78

See merge request !92

Documented configuration file as the default way of running experiments; other small documentation changes and corrections

Merge branch '86-in-evaluate-py-there-is-no-way-of-using-both-4-and-5-column-score-files' into 'master'

Resolve "In evaluate.py, there is no way of using both 4- and 5-column score files"

Closes #86

See merge request !90

Small restructuring and less repetitions

See merge request !91