all: fix Description files

- add missing Build-Depends, Conflicts, Url, Size, MD5sum fields
- add missing 's' to Tag field
- add a space before the dot of the end of description
output: add a flushbybag output option

This option enable to take advantage of event views. If set the output
plugin does flush datas by bags. This enable to have many outputs at the
same date. By the way the gvle plugin that enable the configuration has
been updated inside the GUI. (closes #59)
README: update
output: fix the flushbybag feature

(closes #65)
output: add more precision in float/double output

We improve the float/double representation in file by using the
std::setprecision in std::istream. (closes #67).
de: fix private typedef

The Multiple::MultipleValuesMap type is used in MultipleDbg.hpp but this
typedef is private. Only g++ >= 4.8 detect this error. We fix the
problem: MultipleValuesMap is now public (closes #68).
README: update
decision: fix the plugin clearance

the data structures storing many items are cleared when leaving the
plugin.
(closes #73)
decision: uncomment the ack function signature

In a order to provide more flexibility, the modeling plugin does not
comment anymore the parameters of the acknowlegment signature.
(closes #69)