volume io and server fixes and tweaks

src/mol-io/common/file-handle.ts

src/mol-io/common/simple-buffer.ts

src/mol-io/common/typed-array.ts

src/mol-io/reader/ccp4/parser.ts

src/mol-io/reader/dsn6/parser.ts

src/mol-io/reader/dsn6/schema.ts

src/mol-model-formats/volume/ccp4.ts

src/servers/volume/pack.ts

src/servers/volume/pack/format.ts

src/servers/volume/pack/format/ccp4.ts

src/servers/volume/pack/format/common.ts

src/servers/volume/pack/format/dsn6.ts

src/servers/volume/pack/main.ts

src/servers/volume/server/query/compose.ts