Ledger view - add "export to csv" like button

[aluccaroni]

Add a button to export all the ledger metadata (default and custom) filtered by the search in the page to a delimited text file to enable search and processing outside bkvm.

For security and performance reason no actual data needs to be exportable

Eg: if the page is filtered by OPEN ledger the button need to export all the info of all the OPEN ledger to file