Compatibility with big files, multiple selection, don't overwrite existing devices

Hello. At SOLEIL Synchrotron, we use LogViewer and needed some evolutions. The following changes were made and we would like to have them in official LogViewer :

• SOLEIL TANGOTOOLS-84: added the possibility to select multiple logs
• SOLEIL TANGOTOOLS-85: LogViewer can now open big log files
• SOLEIL TANGOTOOLS-87: Don't override existing device of different class and don't start if the same device is already running

The references TANGOTOOLS-84, TANGOTOOLS-85 and TANGOTOOLS-87 come from SOLEIL's Jira.

A bit more explanations:

• Our users asked us to have the possibility to copy/paste multiple logs at once (TANGOTOOLS-84). So, we enabled multiple selection in table.
• When opening our devices log files, we sometimes had an exception (too many elements). So, we had to deactivate a feature in XML parser (in its factory) to solve that (TANGOTOOLS-85). With that correction, we can now open all of our device log files.
• We discovered that when running LogViewer with a device as argument, it will overwrite what is existing in database, which is very dangerous (TANGOTOOLS-87). So, we avoided that case and the case where a LogConsumer with the same name is already running. In both cases, LogViewer will exit with an error message.
• We also added some eclipse IDE specific files in .gitignore (so that these files/folders won't be committed)