Important changes on data models

Modified model of TimeLineItem by splitting it into several subclasses.
Created and modified DAOs and services related.

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Supplement commit to last commit
Some supplement to TimeLineService

Implemented comparators for timeline and timelineitems
Implemented except addItemToLine related methods
Last commit this morning

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Modified DAO
Modified return values of the insert, update and remove methods in all
DAOs because mybatis has no meaningful  return value of them.
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