added function to convert a DTM object into its representation in "packed DTM" format
added possibility to add DTMs to an existing instance of MicrosliceContents -> data is stored inside when necessary (still contains bugs)
fixed one bug: forgot to move the DTM::data pointer behind the packed DTM header
fixed another bug: initialize vector with 8x zero, not with "8 0"...
added default constructor for MicrosliceContents, to start with an empty one
fixed a bug in an unsatisfying way -> needs design improvement
removed the explanation of the bug that was fixed in the previous commit
fixed public access methods not being const by declaring "cache" variables mutable and private methods also const -> "logical" const rather than "bitwise" const
improved comments
moving the old _dtms into the temporary dtms vector now works
added todo note
updated todo note
grouped constructor for empty MicrosliceContents together with the other methods that cause the data to be owned by an instance, since it makes only sense using this constructor in that case
added option to start dtm indexing from a different value than 0 -> first index must be detected when reading existing data
Merge branch 'master' into add_dtm