Rename "jerasure" to "ec" in pool configuration, function names, fix documentation and Debian build scripts

Old pool configurations with "jerasure" also remain supported as an alias for "ec"

docs/config/pool.en.md

@@ -106,9 +106,10 @@ Pool name.
 
 - Type: string
 - Required
-- One of: "replicated", "xor" or "jerasure"
+- One of: "replicated", "xor", "ec" or "jerasure"
 
-Redundancy scheme used for data in this pool.
+Redundancy scheme used for data in this pool. "jerasure" is an alias for "ec",
+both use Reed-Solomon-Vandermonde codes.
 
 ## pg_size
 
@@ -243,7 +244,7 @@ of the OSDs containing a data chunk for a PG.
 {
   "2": {
     "name":"ecpool",
-    "scheme":"jerasure",
+    "scheme":"ec",
     "pg_size":3,
     "parity_chunks":1,
     "pg_minsize":2,

docs/config/pool.ru.md

@@ -106,9 +106,10 @@
 
 - Тип: строка
 - Обязательный
-- Возможные значения: "replicated", "xor" или "jerasure"
+- Возможные значения: "replicated", "xor", "ec" или "jerasure"
 
-Схема избыточности, используемая в данном пуле.
+Схема избыточности, используемая в данном пуле. "jerasure" - синоним для "ec",
+в обеих схемах используются коды Рида-Соломона-Вандермонда.
 
 ## pg_size
 
@@ -242,7 +243,7 @@ PG в Vitastor эферемерны, то есть вы можете менят
 {
   "2": {
     "name":"ecpool",
-    "scheme":"jerasure",
+    "scheme":"ec",
     "pg_size":3,
     "parity_chunks":1,
     "pg_minsize":2,