support huge number of tables

[eug3nix]

Currently pgmanage becomes slow/unresponsive when the database contains several thousands of tables.
There are several areas to improve:

1. Optimize get_database_meta to load all column data in bulk
2. Optimize database tree node insertion (also do in bulk instead of one by one)
3. Maybe optimize autocomplete initialization when loading huge dataset.

[eug3nix]

most of the optimizations are complete and were included in 1.5
There are some other tweaks done to the html rendering in 837_faster_treeview these should be polished up, tested for stability and probably included in 1.6 release