cleanup files
Fixed Java 1.7 related bug with empty images when embedded into JPanels

merged from https://github.com/VEDAGroup/SHEF/commit/164bbdb312281ec8c6aaaead7160a4058d45ce43?w=1
improved german translation

merged from https://github.com/VEDAGroup/SHEF/commit/61c037224dde0dceaf0378f6009e07c5a687c15a?w=1
Added i18n for target strings in link dialog.

https://github.com/VEDAGroup/SHEF/commit/a20dcb349f03edfaebb8b2a472a68d1dcda0e0d8?w=1
Fixed typos and bad translation in german message properties.

merged from https://github.com/VEDAGroup/SHEF/commit/de7f9b62d5861df3ea6d302acc97349fea2bd4d4?w=1
Added possibility to hide the "hyperlink" image in the hyperlink dialog for better integrability.

merged from https://github.com/VEDAGroup/SHEF/commit/052cc642fb392822816f2dddfb510451824c0a2b?w=1
Make link dialog configurable for better integrability.

merged from https://github.com/VEDAGroup/SHEF/commit/b15a1061c5b932a7258daec1f98ba310ca7cde4d?w=1
Allow hiding of HTML-Editor toolbar.

merged from https://github.com/VEDAGroup/SHEF/commit/2251c360e61933cf4cf06e8bcbc175281d42514c?w=1
README.md updated
README.md updated