AllFilesFilterText, FoldersFilterText and PickFolderQuickLinkText can…

… now be changed after the file browser is initialized, as well

- Changed folderMode parameter to pickMode that supports picking file…

…s and folders simultaneously

- Added optional initialFilename parameter to prefill the filename input field
- Files and folders are now sorted by their names (they weren't automatically sorted on some platforms)
- Made AllFilesFilterText, FoldersFilterText and PickFolderQuickLinkText properties public static so that these labels can be localized or customized
- Write External Storage permission is now added automatically on Android (no manual setup is needed)

File browser no longer throws ArgumentException when entered filename…

… contains invalid characters; filename input field turns red instead

Fixed performance issues that occur when selecting lots of files

- Added context menu that can be opened in 2 ways: a) right clicking …

…a file on standalone platforms or b) clicking the More Options button located at the top-right corner. Context menu has the following buttons:

  - Select All (only when multi selection is enabled and More Options button is clicked)
  - Deselect All (only when more than 1 items are selected and More Options button is clicked)
  - New Folder (closed yasirkula#25)
  - Delete (only when 1 or more items are selected)
  - Rename (only when 1 item is selected)

Bumped version

Added multiple file/folder selection support (closed yasirkula#10)

Note that the Scripting API has also changed slightly with this new feature. The OnSuccess callback now returns string[] instead of string and dialog functions now take an allowMultiSelection parameter (false by default)

Added OpenUPM instructions

Fixed yasirkula#18

Fixed yasirkula#18