clean: Don't use 'fx_assert' macro in 'apps'
Fixed buggy space adjustment algo
Do no allocate slice for file's segmnt0

Avoid the extra meta-block io for most (short) files. Files' slices
begin from segment-1

Signed-off-by: Shachar Sharon <shachars@xxxxxx>
Removed SHA1 code

Prefer modern crypto hash functions like CubeHash

Signed-off-by: Shachar Sharon <shachars@xxxxxx>