Embed assets in elf file (#2466)

* FBT: file_assets generator
* Elf file: process manifest section externally
* FBT, file_assets generator: add assets signature
* Storage: assets path alias
* Flipper application: assets unpacker
* Apps, Storage: use '/data' alias for apps data
* Storage: copy file to file
* Assets: log flag, fixes
* Update f18 api
* Assets: asserts
* Assets: fix signature_data check
* App assets: example
* Example assets: fix folder structure in readme
* Assets: fix error handling
* Assets builder: use ansii instead of utf-8, use .fapassets section instead of .fapfiles, add assets path to signature
* Elf file: comment strange places
* Storage: totaly optimized storage_file_copy_to_file

applications/examples/example_apps_assets/files/poems/theme in yellow.txt

@@ -0,0 +1,19 @@
+Theme in Yellow by Carl Sandburg
+
+I spot the hills 
+With yellow balls in autumn. 
+I light the prairie cornfields 
+Orange and tawny gold clusters 
+And I am called pumpkins. 
+On the last of October 
+When dusk is fallen 
+Children join hands 
+And circle round me 
+Singing ghost songs 
+And love to the harvest moon; 
+I am a jack-o'-lantern 
+With terrible teeth 
+And the children know 
+I am fooling.
+
+source: "https://poets.org/anthology/poems-your-poetry-project-public-domain"