[WIP] Bugfixes and improvments

[xgaia]

[WIP: don't merge now]

I made some improvements in response to user feedback this morning:

• Fix the filter on ID
• Fix numeric detection when values are missing
• Empty values are considered as numeric values
• resetGraph() function instead of reload AskOmics
• This function is triggered when user click on the reset button and at database deletion
• When user upload a new file, results table is emptied
• Database tab instead of stats
• Compute stats at user demand
• When user upload a new file, stats are cleared

new database tab:

With the confirmation button

• Stats on positionable objects

[coveralls]

Coverage increased (+0.03%) to 81.55% when pulling 3497c85 on xgaia:v2.0_improvement into 23cb37b on askomics:v2.0.