Resolve "Allow plugin to hide left panel"

Closes #309 (closed)

docs/plugins/interface.md

+### Interface
+
+#### getOpenedPanel
+
+Return string identifying panel that is currently opened. Available options:
+
+```
+undefined
+'none'
+'search'
+'project-info'
+'plugins'
+'export'
+'legend'
+'submaps'
+'reaction'
+'overlays'
+'bio-entity'
+'comment'
+'available-plugins'
+'layers';
+```
+
+##### Example of getOpenedPanel method usage:
+
+```javascript
+window.minerva.map.data.getOpenedPanel();
+```
+
+#### hidePanel
+
+Close opened panel.
+
+##### Example of hidePanel method usage:
+
+```javascript
+//close specific panel if the panel is opened
+window.minerva.map.data.hidePanel('available-plugins');
+
+//close the panel (regardless which one is opened)
+window.minerva.map.data.hidePanel('available-plugins');
+```
+
+#### OpenPanel
+
+Open specified panel.
+
+##### Example of openPanel method usage:
+
+```javascript
+window.minerva.map.data.openPanel('available-plugins');
+```