change actionbar title to show visiting directory dynamically.

the title shows the current repository or directory user in, 
also clean up the unused string value.
add "no upload tasks" info to UploadTasksActivity

give user a feedback if there are no uploading tasks added to
UploadTasksActivity
remove upload button text and refresh button text in action bar
upload photos to "Camera Uploads" directory only

use cache to ensure no duplicate "Camera Uploads" directory was created
remotely.
change text style in Settings.
fix Camera Uploads issues

change to use remote dirent to ensure no duplicate "Camera Uploads"
directory was created remotely.
clean source code
add remote library delete detection
beautify source code
delete SeafileLibraryChooserActivity use SeafilePathChooserActivity instead.<br>add comments to classes and methods.<br/>keep global variables unsigned, use the default value
clean up source code

delete unused variables, simplify process logic.
code refactor
code refactor
show toast when service starts to function

1. change to show camera upload service started toast and stopped toast
only when the camera upload service starts to function or ends to
function. Instead of showing toast when use turn on or turn off the start
service button.
2. format code, keep a space between 'else' and curly braces
3. correct constant name misspelling
4. rename method to be more readable
Merge pull request #105 from Logan676/lg2

use Camera Uploads folder to upload photos