changes snap button, query buttons and dowload button

[ytorres-cambas]

• Snap button disable after snapping. It is enabled whenever a new point dataset is loaded
• Snapping progress bar reset after snapping
• Tooltips on snap button and query button when disable. These tooltips indicates that and action must be done first in order to enable these buttons
• download button visible after snapping. If a new dataset is loaded after snapping, download button is hidden